Say you have low compression, or a blown head gasket (between cyclinders) for example. Will the unburned air/fuel charge look like a lean condition (high oxygen content) to the O2s? Thus causing the computer to crank up the pulse width on that side. I thought I fixed my exhaust leak, got spark and fuel on all 8, but still got a similar problem. Computer thinks bank 2 is running super lean and has a Pulse width almost double bank one to make up for it.

I know, I know just check the compression already. I'll get there eventually

Thanks
Sean

 

A miss ususally looks lean to the PCM, because the 02 sensor sees all that unburned oxygen, it cannot read the fuel at all.

So what generally happens is it adds more fuel trying to correct the "lean" condition. It will be rich out the pipes but read lean.